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Jan. 27, 1931. e. SPERTI ET AL 1,796,286

' ELECTRONIC TUBE Filed June 12, 1925 11/ 4 16 i 17 cm 15 3 O i'llllllllIL 1L :IILLII wvEN'fdRs LQK ATTORNEYS Patented n. 21, 1931 UNITED STATESPATENT OFFICE GEORGE SPERTI, OF GOVINGTON, KENTUCKY,AND LOWELL M.ALEXANDER, OF CIN- OINNATI, OHIO, ASSIGNORS OF ONE-TENTH TO ALLEN &ALLEN- (A FIRM COM- POSED OF ALFRED M. ALLEN AND MARSTON ALLEN), OFCINCINNATI, OHIO ELECTRONIC TUBE Application filed June 12, 1925. SerialNo. 36,706.

It is our object to provide electronic tubes suitable for use with anenergizing current from the usual domestic light circuits, whetheralternating or direct, and also to provide an electronic bulb which isvaluable for use with the usual electrolytic cells, now generallyemployed in radio work.

One of our objects is to provide a tube in which oscillatory variationsdue to difference in potential of portions of the electron emitting andcontrolling elements are largely eliminated.

'Our object is also to provide a bulb in which disturbances due toalternating current as av generating source, and arising chiefly whenthe thermionic effect of the elec tron discharge element is reduced dueto moments of zero current, are so eliminated as to do away withdistortions within the audible range.-

Thus we preferably employ as a generating electrode, an element havingbranches of high resistance connected to an intermediate portion of amaterial of comparatively low resistance and high thermionic effect,which intermediate portion serves as the generating body for theelectrons on which the tube operates.

We are enabled to require a very low watt consumption by this means,because we obtain a large portion of our heating effect by passing theenergizing current through the said intermediate portion, whereas in theprior art with which we are familiar, the thermal effects of the currenthave been aplied uniformly to a filament portion which imparts itsheating to a thermionic member by heat conduction alone.

Also we may shield the high resistance portions of our filament, orelse'form these portions of non-thermionic material and do not have toprovide extra leads within our tube, in order to connect up thegenerating electrode in the out-put circuit of the tube.

Furthermore, we preferably make our electron generatin element'a spot,and thus can use small grid? and plates, and the tube elements thus havefairly equipotential surfaces, and the range of efl'ectiveness'of smallpoten- 50 tials as impressed on the grid makes our tubes of higheffectiveness in both rectifying and amplifying. Furthermore internaltube capacity effects will be reduced to a minimum between theelectrodes of the tube due to the small dimensions of the electronsource.

We accomplish our objects by that certain construction and arrangementof parts to be hereinafter more specifically pointed out and claimed.

In the drawings:

Figure 1 is a diagram of a typical tube involving our invention.

Figure 2 is an elevation of a generating electrode of another pattern.

Figure 3 is an elevation of another type of electrode.

Figure 4 is a perspective diagram of still another type of electrode.

Figure 5 is a perspective diagram of a form to give increased heateffect, and showing a single tube with a. hole in it, to serve as ashield. r

The electronic bulb is shown mainly in diagram, as itvdoes not differ asto grid and plate from the usual tube except in proportions, which. willbe a variable in any event.

We indicate by the outline 1 the glass tube, within which a desiredvacuum has beenset up. The usual grid is indicated at 2, and the late at4. p

T e novel electrode is shown in Figure 1, as composed of two relativelyhigh resistance filament sections 5 and 6, preferably of equal lengthand balancing disposition, connected together by a comparatively lowresistance element 7. The balancing or equality of the filaments is notof primary importance. The size of the filaments should not be so out ofproportion, however, as to prevent a heat flow from each filament to theelement 7. We have indicated bent tubes 8 and 9 of glass or othermaterial, surrounding and shielding against electron flowthe balancedfilament sections, but leaving the connecting spot exposed. These tubesmay be grounded as in.- dicated at 8a, but being of large area will notdistort the action-0f the electron stream due to impressed charges.

The connections from this electrode are indicated at 11 and 12, aspassing out through the bulb, where they join the incoming leads 13 and14 from the source of current, which may be alternating or direct, suchas is transof a lightmitted in the usual service lines and powercompany.

The connections 11 and 12 are indicated as bridged by an impedance 15,to which the leads of the grid and plate circuitsare con nected, asclosely to a full intermediate 'po'- sition as practical. The platecircuit in the drawing includes the leads 16 from the plate to theprimary coil 17, to the B batteryT1h8f and lead 16a to the impedance 15.point of connection to the impedance 15, shown here as a resistance willbe arranged to balance the potentials so as to bring the lead and hotspot to the same potential. The

grid circuit in-the drawing includes the lead 19 from the grid to thesecondary 20 and from it to the same connection as the plate circuit, tothe resistance 15. These are merely' shown as an example of one-kind ofpossible circuit for the tube elements.

In operation this bulb providesa steady electron flow from thegenerating electrode in which no audible variations appear. The

c rrent, assuming it tobe alternating, causes I t e filament sections toglow most-brightly atthe two crests of the alternations, and to dim downat the neutral-points between oscillations. The'central' spot because ofits cross section or inherent composition, is not brought to a glow bythe current alone, but

. the heat moving by conduction into the spot from both filaments keepsthe spot glowing and discharging electrons right through the zero periodof cycle of the current. The heat conducted by the two filament sectionsto the connecting spot moves in at both sides to the spot which retainsits heat due to its nature, so that there .is no appreciable. drop inglowof the spot, orof electron flow there-' from, -whenthe filamentsections oscillate in brilliance.

In,F igure 2 we have indicated a similar electron generating body tothat in Figure 1,

and having the filament sections 5 and 6, but the central hot spot has anodule of oxide at the center as indicated at 21, whereas the filamentsections are not thermionic. In

Figure? is indicated an electrode having a pair of filaments of metalsuch as platinum (not thermionic) connected by a hot spot of anothermetal such as thoreiated tungsten, which is thermionic. In Figure 4 isindicated an electrode in which the filament sections are very thinribbons, with ath icker central section or hot spot formed of a desiredshape. I

In each instance the heating effect of the current is not productive ofa practical electron discharge on the connecting element'or filaments,and it'is from the hot spot'that the electron stream on which the tubeoperates is discharged.

In the form shown in Figure 5 the filament sections are formed intocoils at 20, 20, and the whole device is surrounded by a U tube 21*,which has an aperture 22 for the electron stream. The heating effect isincreased by the coiling of the filaments with regard to the conductedheat to the thermionic spot. In use the form of tube shown will probablynot collect a charge that will affect the electron stream, and if itdoes a simple grounding will eliminate this effect. In the forms ofelectrode in which no shields are shown, it will probably be best to usea shield in order to prevent the charges on the non-ther- -mionicfilament portions from having any control on the electron stream. In abalanced arrangement of filament sections, however, theopposed directionof the two sections would result in a cancellationof the charges to acertain extent.

In use with A batteries in radio, our tubes eliminate distortions due tobubbling in the battery, in the same manner as they eliminate theaudible variations due to an alternating current energizing source. Thetubes of our invention may be applied to a wide range of uses, whereverit is desired to control the flow by the energizing current source, andis maintained at proper thermionic stage durin periods of zero currentby its own retained eat, and also b conduction from portions of thefilament w 'ch in one way or anther are pre-' vented from afiecting theplate current.

Having thus described our invention, what we claim as new and-desire tosecure by Letters'Patent, is

An electronic vacuum tube having a grid and a plate, an electrongenerating electrode ,to be connected to the grid and plate comprisingbranch elements of high heating effect due to electric current, and anintermediate electron emissive element in series electrically with thebranches and of relatively low heating efiect but high thermal ca acity,

'said intermediate element being the so e electron discharging means ofthe tube.

GEORGE SPERTI. LOWELL M. ALEXANDER.

